Sound waves could replace breast biopsies

A system that uses sound waves to "prod" suspect lumps deep within the body could save millions of women from the trauma of a breast biopsy.

The hope is that the technique, under development at Duke University in Durham, North Carolina, will use ultrasound waves to distinguish malignant tumours from benign ones by measuring their elasticity.

Currently, suspect lumps are found using X-ray mammograms, ultrasound or through physical examination - but these methods can only locate the growth. The only way to be sure whether it's malignant or not is to perform a biopsy - surgically removing part of the lump.

"In the US, the percentage of biopsies that are performed on benign breast lesions is between 60 and 80 per cent," explains Katherine Nightingale, head of the Duke team. Figures are similar in Europe.

"There are no clinically available imaging methods that provide information about the mechanical properties of tissue," says Nightingale.

Pressure pulse

The Duke team uses a hand-held ultrasound device to locate and measure the stiffness of lumps by nudging them. "We are finding that different tissue types respond differently," Nightingale says. The team discovered that malign and benign lesions resist prodding to very different degrees and recover their shape at different speeds.

Their device intersperses conventional low-powered ultrasound bursts, used for locating lumps, with much higher-powered "pushing" beams (see Graphic). The higher pressure creates an acoustic force that moves the tissue very slightly, typically between 10 and 15 micrometres.

The tissue stiffness is inversely proportional to the amount it moves, which can be calculated using the ultrasound beams. "We are investigating the potential for using both of these parameters to differentiate benign from malignant lesions," says Nightingale.

Brief encounter

Their device could offer a quick and safe way to spot benign lumps without surgery. And it can easily be added to existing ultrasound scanners used for locating lumps.

It's safe, says Nightingale, because the high-power pushing pulses last no longer than a millisecond and are only applied locally. This prevents the tissue from getting hot.

"If it's successful it would be a tremendous leap forward," says Stephen Duffy at the Imperial Cancer Research Fund in London. "But you would want to be absolutely sure that it didn't miss malignant tumours."

Biopsies are not as uncomfortable as people think, he says, although it's nicer not to have a needle stuck in you.

More at: Journal of the Acoustical Society of America (vol 110, p 625)

If you would like to reuse any content from New Scientist, either in print or online, please contact the syndication department first for permission. New Scientist does not own rights to photos, but there are a variety of licensing options available for use of articles and graphics we own the copyright to.